Erroneous results during service discovery of custom UUIDs

RE: Erroneous results during service discovery of custom UUIDs

Userta — Thu, 13 Jun 2019 07:46:08 GMT

Much thanks for your inputs. I will shortly get to try out these things.

RE: Erroneous results during service discovery of custom UUIDs

Hung Bui — Tue, 11 Jun 2019 09:02:58 GMT

Hi Tejinder,

The db_discovery module should work with custom UUID as you can see in the ble_app_uart_c example.

To increase the speed of service discovery, please make sure you have low connection interval. The fastest connection interval is 7.5ms.

If you can capture a sniffer trace of the process, it would be easier to identify if there is any other reason why it's slow.

RE: Erroneous results during service discovery of custom UUIDs

Userta — Thu, 06 Jun 2019 08:55:06 GMT

Hi Hung Bui, thanks for your inputs. good to know about the private mode.

My problem is this: i have used by-the-book implementation i.e., the standard GATT procedures as described in the SDK mesage sequence charts and i have tried to use sd_ble_uuid_vs_add(), whereever possible. But i still have the problem. I will have a look into my source code again and confirm about sd_ble_uuid_vs_add() once again. An additional problem is that the service discovery of a single service lasts about 8-10 seconds, not sure why it's taking so long (could it be that mulitple GATT read prcoedures done with "sd_ble_gattc_read()" for custom UUIDs contribute hugely to the time needed to conclude the discovery procedure?)

i have been using the standard service and discovery API's from the Nordic SDK. i am aware that there is also "db_discovery" library module offered in SDK. but i am not sure if this could also work for GATT structure with custom UUIDs. could you pls suggest, if the db_discovery module can be use for custom UUIDs and is it preferable over the standard API's (from the sequence charts above)?

Much thanks for your time!

RE: Erroneous results during service discovery of custom UUIDs

Hung Bui — Wed, 05 Jun 2019 15:01:10 GMT

Hi Tejinder,

If you need to upload confidential code, you can convert the case to private case. Please click on "Go Private" button above.

Please try to test with one single service and one characteristic first.

I had a look at your code and could be a little bit hard to understand fully because I'm not very familiar with the code you provided.

Please be aware that sd_ble_uuid_vs_add() should only be called to add the UUID base into the database, and it's important to use corresponding ble_uuid.type when calling sd_ble_gattc_primary_services_discover() or sd_ble_gattc_characteristics_discover().

Make sure you call sd_ble_uuid_vs_add() for all of the 128 bit UUID base you plan to disconver, prior to the service discovery.

Please follow these message sequence chart for service discovery and characteristic discovery.

RE: Erroneous results during service discovery of custom UUIDs

Userta — Tue, 21 May 2019 14:33:47 GMT

Hi there,

much thanks for your prompt response. I will get back to you tomorrow with my source-code. Till then,

kind regards,

RE: Erroneous results during service discovery of custom UUIDs

Hung Bui — Mon, 20 May 2019 15:02:18 GMT

Hi Tejinder,

We need to have you code to know what could be wrong. Also please provide information about your 128 bit UUIDs.

I would suggest you to test with 1 service and 1 characteristic first before testing with multiple characteristics. You can refer to the ble_app_uart_c for reference

Note that the uuid-type (equivalent to our uuid_type in our code I assume) is the index of your base UUID in the UUID database inside softdevice.

When you register your first 128 bit UUID base you will have uuid_type = 2 (Vendor begin)

When you register your 2nd 128bit UUID base, you will have uuid_type =3 for that UUID base. And so on for next UUID bases.

You would need to register the UUID base you are expecting to discover on the peer device in advance. Otherwise you would need to do extra step to read the UUID value. It's not covered in the discovery library.